1. Field of the Invention
This invention relates to a method for making a condenser microphone, more particular to a method for making a diaphragm unit of a condenser microphone using liftoff techniques.
2. Description of the Related Art
Various methods and materials have been used for fabricating condenser microphones. A silicon wafer is normally used and is patterned by etching and deposition so as to form layered structures, such as a diaphragm and a back plate of the condenser microphone, thereon when using semiconductor techniques to fabricate a condenser microphone. U.S. Pat. No. 5,573,679 mentions a single-wafer process and a two-wafer process for fabricating a condenser microphone. In the two-wafer process, the diaphragm and the back plate are formed on separate silicon wafers, which are then bonded together. After bonding, the pair of the wafers is diced into individual capacitor devices for making condenser microphones. In the single-wafer process, after formation of the layered structures, the silicon wafer is also required to be diced into individual capacitor devices.
The aforesaid conventional methods are disadvantageous in that the individual capacitor devices thus formed are likely to be damaged due to the dicing operation, which results in a decrease in the production yield.